I met a lot of girls with boyfriends that were still attacted to me. In my experience, they will all (or almost all) resist you to some extent when you try to move things forward with them sexually (such as kiss them), explaining that they're in a relationship. But here's where you have to use your judgment. If you think they like you, but they love their boyfriend, don't want to break up with him and would never cheat on him (or it would really break them afterwards), then I think it's best to just leave it be, at least unless the relationship comes to an end or she changes her mind and starts pursuing you herself.
However other times the girl really likes you and is open to something even though she's in a relationship. She will probably still resist you, but it's mostly token resistance. She doesn't want to feel bad by cheating on her boyfriend too easily, but secretly she wants you to overcome her resistance and take her anyway. Then at least she can say to herself that it's not really her fault and that it "just happened".
It all depends on how much she really likes you, what kind of girl she is (and how experienced) and how serious she views her relationship as.
From what you're saying, it looks like it could very well be the second case, so why don't you try to make a move and find out? Even if she rejects you, I don't think it's a problem if you REALLY just want to be friends with her after, as long as you're cool about it and don't make it a big deal.
If you don't think she'll be willing to come to your place right away, you can just try to meet-up in a café or something and take her home later on, that's not a big deal IMO.